Heel attaching with resin mixtures



P 1 959 E. E. JOINER ETAL 2,901,841

HEEL ATTACHING WITH RESIN MIXTURES Filed July 16, 1958 In ven tors Ed gaPE Joiner John, P Szumski United States Patent HEEL ATTACHING WITH RESIN MIXTURES Edgar E. Joiner, Andover, and John P. Szumski, Marblehead, Mass, assignors to Fred W. Mears Heel Company, Inc., Lawrence, Mass, a corporation of Massachusetts Application July 16, 1958, Serial No. 748,960

Claims. (Cl. 36--24.5)

This invention relates to attachment of heels to shoes, and particularly to a method for attaching heels to shoes which does not require the use of permanent metallic fasteners.

' The usual method of attaching a heel to a shoe is by a metallic fastener such as a nail or screw which must be inserted by complicated and expensive machinery. Such customary fastenings present disadvantages in many styles of shoes, particularly womens shoes. A metallic fastening in a shoe creates a rough, uncomfortable surface at the heel seat where the clinched fastening is covered with a thin lining. Such a metallic fastening tends to corrode, causing staining and deterioration of the leather and often tends to Work loose, while in use, puncturing the lining and irritating the wearers heel. If the fastening for a currently fashionable narrow thin heel is large enough to be secure, it may be so large as to split such a slim wooden or plastic heel, resulting in an expensive reject or an unsafely attached heel.

In an attempt to overcome the undesirable features of the mechanical fasteners, various methods to attach a heel to a shoe using a plastic rather than a mechanical bond have been suggested, for example in United States Letters Patent No. 2,299,195, granted October 20, 1942, on an application filed in the name of A. E. Ushakoff, and No. 2,447,512, granted August 24, 1948, on an application filed in the name of J. F. Leahy. But such methods require some additional mechanical adaptation, such as physically shaping the heel or shoe upper to provide an interlocking relationship between the plastic and the heel and heel seat. This involves an expensive departure from conventional shoe and heel manufacturing methods. Heel attaching by injection of the plastic material requires a hollow heel with its accompanying structural Weakness. The handling of the plastic material itself has proven to be a problem. Even with the shoe bottom and the heel clamped together, it is found that the fluid plastic may stiffen to a degree which prevents complete filling of spaces and bonding of surfaces or on the other hand may exude from between the shoe parts before suflicient pressure can be exerted to force it into the crevices and recesses to bond the shoe parts into a unitary structure.

It is the general object of the present invention to provide a method of attaching a heel to the heel seat of a shoe in a unitary strong, light, rigid structure. It is a further object of the invention to provide a method of joining a heel, especially a solid plastic heel, to a shoe with a plastic material by a relatively simple and inexpensive method which does not require complicated or expensive machinery and which is adaptable to mechanical assembly line technique. It is a further object of this invention to provide a shoe with an interior heel seat of permanently smooth surface construction presenting a more comfortable wearing article of footwear.

We have found that a heel and heel seat of a shoe may be strongly and firmly united in a continuous unitary structure by inserting into a recess provided in the ice top face of the heel, a special plastic material selfexpandable to form a heavy-walled cellular structure having exceptional resistance to crushing under localized pressure. The heel is assembled against the heel seat and the plastic material is expanded by internal pressure to fill the void between the heel and heel seat of the shoe and to Wet and bond the entire surface areas in the recesses contained between the peripheral rim of the heel and overlasted upper, thus filling the entire width of the heel-seat area. The expanded plastic material is then cured to a hard rigid body permanently and strongly bonding the parts into a unitary structure.

The features of this invention are further illustrated by a description of the accompanying drawings.

In the accompanying drawings,

Fig. 1 is an angular view of a heel and shoe before heel-attaching;

Fig. 2 is an elevational view on a reduced scale of the heel and shoe held in assembled relationship by clamping mechanism;

Fig. 3 is an elevational view partly in section of the heel section of a lasted shoe with the heel secured by expanded resin according to the present invention;

Fig. 4 is a transverse vertical cross-sectional view taken on line IVIV of Fig. 3; and

Fig. 5 is an elevational view partly'in section of the heel section of a lasted shoe with the heel temporarily secured by a removable fastening agent during the permanent attaching process.

A heel 12 useful in the process of the present invention, as shown in Fig. 1, is formed with a recess 14, in the heel-seat engaging surface 16, which surface flares outwardly toward the peripheral rim 34 of the heel 12. A ridge 48 is provided along the heel breast edge of rim 34 to provide a substantially fluid tight seal when pressed against the shoe bottom. The recess 14 is of a size to provide a volume large enough for effective expansion of the filling and bonding resin mixture. The outward flare of the top surface 16 offers a generous surface area for the bonding of upper 10 and heel 12 by the resin.

The shoe upper 10 is of conventional design with the sole 18 terminating at 20 in the vicinity of the heel breast. A special steel shank 22 provided with an offset portion 24 extends beyond the sole 18 into the heel-seat portion 26 of the shoe upper 10 so that it will project into the heel recess 14 when the heel and shoe upper are assembled (see Fig. 3) and be embedded in the expanding resin. It will be understood that conventional shanks may be used and be bonded by the expanding resin to provide a firm union between resin and shank. The overlasted margin 28 of the shoe upper is secured by lasting tacks 30 which are driven around the rim of the heel seat in the conventional manner. This marginal area provides an advantage to the bonding action of the resin mixture by offering many small recesses 32 around the tacks 3th and the crevices formed in lasting the shoe, to receive and hold the resin. When the shoe upper 10 and the heel 12 are joined in opposing relationship, the recess 14 and the heel seat portion of the shoe upper 26 define a closed chamber to contain the resin mixture.

The special resin mixture which is the unifying mechanism of the present invention is a combination of expandable thermoplastic particles or beads preferably polystyrene beads and a liquid thermosetting resin, with a curing agent for the thermosetting resin. The method adding the curing agent, also at room temperature, and stirring the entire mixture to uniform' consistency.

The expandable polystyrene beads preferably employed" are known per se and comprise a base of styrene polymer 3 with-a volatile organic liquid which is a non-solvent for the polymer absorbed therein, and homogeneously dispersed throughout the beads. Upon heating to the boiling point of the organic liquid, but below the soften- "pointer the polymer, the liquid volatilizes and, in a, closed mold," expands the styrene polymer into a cellulair substance. Such expandable polystyrene beads are disclosed in United States Letters Patent No. 2,744,291,

granted MayB, 1956, in the name of Fritz Stastny, and

. of these. The polyepoxides are complex resinousmatcrials. and may be produced by the reaction .of polyhydric phenols with a polyfunctional chlorohydrin such as epichlorohydrin and glycerol dichlorohydrin. The preparation of epoxide resins is shown in United States PatentsNos. 2,506,486 to Bender et al., granted May 2, 1950, and- 2,589,245 to Greenlee, granted March 18, 1952.

The epoxide resins used in the present invention are liquid atroom temperature, with aviscosity at.25 C. of from about 3600 to 15000 cps. The range. of epoxyv equivalentsois from about 17 0 to 210 and the molecular weight is between 340 and 400. Such epoxy resins are commercially available as Epon 828 or 820, made by the Chemical Division, Shell Union Oil Co., and Aral- 6005, made by the Ciba Company, Inc.

7 The epoxide resin is curable to a hard, strongstate bytheaction of a catalyst, such as the aliphatic primary or secondary amines having a molecularfweight of at least 100. Included in such amines are ethylene diamine, triethylene tetrarnine, and dimethyl amino propyl amine.

Amodifying agent which may be a high boiling alcohol may be used to secure uniformity of reaction.

The proportion of thermosetting resin relative to the beadsis preferably high enough to ensure development of suflicient exothermic heat ofreaction to cause effective, expansion of the beads to force the resin into him contact with the surfaces of; the heel and heel seat. It is also important that there be enough thermosetting resin to flow into the narrow crevices and recesses of the, assembly to secure all-over bonding of the heel to the. heel seat. Suitably there will be used from about l.to about2 parts by weight .of expandable beads to one part by weight of the liquid thermosetting .resin.

Themixing procedureemployed Where polyepoxide resin is used involves heating the epoxide resin to 150 to 190 F., preferably from 180"v to 190 F., adding the polystyrene beads at room temperature, and quickly stirring the mixture to insure uniformly wetting the exteriorsurfaces of the beads with the warm epoxide resin. The curing agent, also at room temperature, is stirred vigorously into the combination, and finally the modifier is added and the entire mixture stirred to uniform condition.

The warm resin mixture is deposited in the recess 14 of the heel 12. The epoxideresin curing reaction generates su flicient heat to increase the temperature of the mixture to cause expansion of the polystyrene beads. This requires-a compact'body of a substantial quantity ofthe resin mixture so that the heatgenerated will not' escape too rapidl-y. If there is-too rapid a transfer of the heat frpm-thereaction, the mixture will not attain a temperature'high enough to cause the uniform expansion of the polystyrene beads by the 'volatilization of the organic liquid occluded in the beads.

With a mass of this resin contained in the heel recess 14, the heel 12 is assembled against the shoe upper 10 of a lasted shoe, as in Fig. 2, thus defining a closed chamber, and is held in position by a clamp 36, for a period of suificient duration to allow the polystyrene beads to expand from internal pressure and the resin to cure. The polystyrene beads expand into a body having fine cellular structure, with each cellular body surrounded by a film of the epoxide resin thus forming a thicker walled cellular structure which serves as binder and reinforcement. The expanding beads drive the epoxide resin outward to coat and adhere to the surfaces it contacts. The entire process from placing the resin mixture in the heel recess 14 to removing the assembled shoe from the clamp may require a matter of from 2 to 20 minutes. The time and the degree of bead expansion may be controlled to some extent by the preheat temperature of the epoxide resin.

Figs. 3 and 4 show the polystyrene beads 38 expanded. by the heat developed by the catalytic polymerization of. The expanding beads increase the the epoxide resin. volume of the resin mixture until it fills the entire cavity and surrounds the shank 22, wetting and strongly adhering to all the surfaces it contacts. The expanded polystyrene beads 38 are themselves too large to pen eitrate the slim crevices between the heel 12and the shoe upper 10, but the increase in volume forces the fluid epoxide resin itself free from the beads into the recesses 32 and into these crevices out to the feather edge 40, depositing a thin layer of solid resin 42, forming an As it isextremely strong joint at these edge portions. cured, the resin is bonded in an interlocking relationship to the surface of the recesses 32 provided in the shoe parts.

The special steel shank 22 with the offset portion24 is firmly embedded in and held by lthe expanded resin mixture. The thick cell walls of thermoset resin surrounding the expanded thermoplastic resin particles are strongly resistant to crushing and hold the shank rigidly to the heel and shoe. The epoxide resin between the heel seat and the heel cures to form an extremely tough .bond

engaging the area of the overlasted upper 28 andfilling all the recesses 32 contained therein out to the feather edge 40. All the voids between heel and shoeare thus filled to present a continuous, solid attachment ofheel to shoe and an all-over support for the Wearers heel while contributing to comfort.

As shown in Fig. 5, an alternative device for holding I heel 12 and shoe 10 together is a temporary heel; attach ing member such as a nail or screw 44 extending through; the insole 46 at the heel seat and extending into the heel. This device has the practical advantage of elimimating the need for special clamps. Also, the shoe may be handled for breast flap work while the resin is curing. The use of a temporary nail or screw permits the rapid assembly of shoe and heel parts which may be removed. when convenient or left in place if further mechanical,

strengthening of the bond is desired and it is not. detrimental to the appearance of the finished shoe. The invention is not limited to using clamps, nails orscrews but may use any other device to. hold shoe upper and heel in immovable relationship until the resin mixture has cured into a tight rigid bond.

The following example is given. to aid in understanding the present invention, but it is .to be understood that.

theinvention is not restricted to the specific composition and procedure described below:

The epoxide resin was a glycidyl polyether liquid at room temperature with a viscosity at 70 F. of 8,000 cps. and at 170 F. of 80 cps, and a specific gravity at 25 C. of 1.2. It had a reactivity range of epoxy equivalents of 173-179. The expandable polystyrene beads had a range in diameter of from 1 to 1.5 mm., with an average of about 1.4 mm.

The epoxide resin was heated to about 170 F. and the polystyrene beads, at room temperature, were added and stirred in rapidly so as to insure uniform wetting of the exterior surfaces of the beads with the liquid resin, thereby allowing the beads in expanding to be reinforced by films of the thermosetting hard epoxide resin which forms a thicker walled cellular structure. The curing agent, at room temperature, was then stirred vigorously into the combination, and finally the alcohol was added, and the entire mixture stirred to uniform condition.

5.5 ml. of the liquid mixture while still but was deposited in the recess of a size 7 heel for a shoe, as described above, and the heel was then clamped to its corresponding overlasted upper which was provided with a shank stiffener, as previously described. The clamp was removed after ten minutes, at which time the mixture had expanded and solidified. When examined the following day, the heel, shank stiffener and shoe upper were found to be firmly and strongly united together by the expanded and hardened resin and the interior heel seat. presented a smooth surface. When the shoe was cut open, it was found that the original volume had expanded from 5.5 ml. to a volume of roughly 15 ml.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. A method of permanently attaching a heel to a shoe, which comprises providing an overlasted upper of a shoe and a heel having a recess in the heel-seat engaging surface, depositing in said recess a quantity of a fluid resin mixture comprising a liquid thermosetting resin and particles of a thermoplastic resin containing therein a blowing agent, assembling the heel in opposing relationship to the heel seat of the overlasted shoe upper thereby defining a closed chamber, holding said heel and heel seat together, supplying heat to cause gases to evolve from said blowing agent contained in said particles of thermoplastici resin to expand said particles to increase the volume of the resin mixture to fill said chamber and force portions of the liquid thermosetting resin by internal pressure into crevices between the heel and heel seat of the overlasted shoe upper, and maintaining the heel and overlasted upper in opposing relationship until the liquid thermosetting resin mixture has cured into a hard rigid body uniting the heel and shoe into a unitary structure.

2. A method of permanently attaching a heel to a shoe, which comprises providing an overlasted upper of a shoe including a shank stiffener with an end extending into the heel-seat portion, providing a heel having a recess in the heel-seat engaging surface, depositing in said recess a quantity of a fluid resin mixture comprising a liquid thermosetting resin and particles of a thermoplastic resin containing therein a blowing agent, assembling the heel in opposing relationship to the heel seat of the overlasted shoe upper thereby defining a closed chamber with the end of said shank stifiener in said chamber, holding said heel and heel seat together and supplying heat to cause gases to evolve from said blowing agent contained in said particles of thermoplastic resin to expand said particles to increase the volume of the resin mixture to fill said chamber and surround said end of said shank stiffener and force portions of said liquid thermosetting resin by internal pressure into crevices between the heel and heel seat of the overlasted shoe upper, and maintaining the heel and overlasted upper including the shank stiffener in opposing relationship until the liquid thermosetting resin mixture has cured into a hard rigid body unit- 6 ing the heel, shank stiffener and shoe into a unitary structure.

3. A method of permanently attaching a heel to a shoe, which comprises providing an overlasted upper of a shoe and a heel having a recess in the heel-seat engaging surface, depositing in said recess a quantity of a fluid resin mixture comprising a liquid resinous glycidyl polyether, a curing agent for said resinous glycidyl polyether, and expandable polystyrene beads containing therein a homogeneously dispersed volatile organic liquid whose boiling point is lower than the softening point of the polystyrene, assembling the heel in opposing relationship to the heel seat of the overlasted shoe upper thereby defining a closed chamber, holding said heel and heel seat together, supplying heat to volatilize said organic liquid dispersed in said polystyrene beads to expand said beads to increase the volume of the resin mixture to fill said chamber and to force portions of said liquid resinous glycidyl polyester by internal pres- 20 sure into crevices between the heel and heel seat of the overlasted shoe upper, and maintaining the heel and overlasted upper in opposing relationship until the resin mixture has cured into a heavy-walled crush-resistant cellular structure constituting a hard rigid body uniting the heel and shoe into a unitary structure.

4. A method of permanently attaching a heel to a shoe, which comprises. providing an overlasted upper of a shoe, providing a heel having a recess in the heelseat engaging surface, depositing in said recess a quantity of a fluid resin mixture comprising a liquid resinous glycidyl polyether, a curing agent for said resinous glycidyl polyether, and expandable polystyrene beads containing therein'a homogeneously dispersed volatile organic liquid whose boiling point is lower than the softening point of the polystyrene, the deposited resin mixture constituting a body of suflicient cross section that exothermic heat evolved in curing the glycidyl polyether causes expansion of said polystyrene beads, assembling the heel in opposing relationship to the heel seat of the overlasted shoe upper thereby defining a closed chamber, holding said heel and heel seat together, and by the exothermic heat of the curing reaction volatilizing said organic liquid dispersed in said polystyrene beads to expand said beads to increase the volume of the resin mixture to fill said chamber and to force portions of said liquid resinous glycidyl polyether by internal pressure into crevices between the heel and heel seat of the overlasted shoe upper, and maintaining the heel and overlasted upper in opposing relationship until the liquid resin mixture has cured into a heavywalled crush-resistant cellular structure constituting a hard rigid body uniting the heel and shoe into a unitary structure.

5. A method of permanently attaching a heel to a shoe, which comprises providing an overlasted upper of a shoe including a shank stiffener with an end extending into the heel-seat portion, providing a heel having a re: cess in the heel-seat engaging surface, depositing in said recess a quantity of an expandable fluid resin mixture comprising a liquid resinous glycidyl polyether, a curing agent for said resinous glycidyl polyether, and expandable polystyrene beads containing therein a homogeneously dispersed volatile organic liquid whose boiling point is lower than the softening point of the polystyrene, the deposited resin mixture constituting a body of sufficient cross section that exothermic heat evolved in curing the glycidyl polyether causes expansion of said polystyrene beads, assembling the heel in opposing relationship to the heel seat of the overlasted shoe upper thereby defining a closed chamber, holding said heel and heel seat together, and by the exothermic heat of the curing reaction volatilizing said organic liquid dispersed in said polystyrene beads to expand said polystyrene heads into cellular bodies, said cellular bodies being surrounded by and embedded in a continuous phase of said resinous s ysidylpe yeth rr the :exp n ionof aid.- eas s increas: i ing the volume of said resin mixture to fill said, chant-,1

her to force portionsofs idliquid resinq sglycidyl p yether by internal (pressure intocreyices betweenthe heel andkheel'iseait of the .oyerlasted shoe upper,. and .main-. raining. the. heel and, overlasted 1 upper in opposing relae tiqnship -untilithe liquid resinmixturehascured into a, boggy-walled crush-resistant cellular structure. COIISflf-Utr.

ingja hard rigid bodyruniting the heel and, shoeinto; a

structure.

6. 'A method; of permanently, attaching a heel to a shoe, which .comprisesproviding an .oyerlasted upper of a shoeandia heel havinga recess in the heel-seatrengaging; surface, depositing in said recess a quantity of a fluid resin mixture comprising aliquidresinous glycidyl polyether, 8. curi l l ent for said resinous glycidyl polyether,

andcxpandable polystyrene beads. .conta-ining therein a homogeneously. dispersed volatile organic liquid whose point, is lower than the. .sotten ng. Point of the polystyrene, assembling. the heel; in-- opposing. relation- ShjPgtOgthC heel seat. of theoverlasted shoe upper thereby defininga. closed chamber, in ert-ingzal mov bl .n echanicalfastening means through said heel seat and into said heelto .holdsaid heel and heel seattogether, and by the exothermic heat, of the :curing reactionyolatilizing said organic liquid dispersed in said polystyrene beads to expandsaid beads to increase the volume of the resin mixtureuto fill said chamber. andto force portions of said liquid resinous. glycidyllpolyeth er byinternal pressure into; crevices between the, heel and vheelrseat of the overlasted sh e= ppn nd rn ntaining. he. he l, n v r:

lasted-upper insaid opposing relationshipuntil; the liquid gresin mixture. has cured into a heayywwalledfcrush l resistant. cellular structure constituting a hard rigid; 35

uniting the heel and shoe into a unitary structure.

the heQl-Sfiflt. engaging surface, and a body of thick-walled out intmthe; crevices I between the-.heel and heel-seat to holdisaid' heel shank stifiener' and shoe:.upper-firmly to-.

gether.

8.11m combination,- a shoeuppen a heel attached to: saidlupper, .saidheel' having a recess in. theheeLseat. engagingsurfaceand a body. comprising particlesof a.

fine cellular thermoplastic resin surroundedibyandzerm bedded'rin va1 cured thermosetting resin,-.filling said recess andoadhering.to; the.,walls ofisaid-irecess and :to :the heel seatiof said shfoempperand portions of said cured thermosett'ing resin substantiallyfree from particles .ofsaid fine cellularthermoplasticresin extending. out into the. crevices i between. the. heel and;heel-seat to hold said heel and shoe upper firmlytogethen 9'."In combination, a shoe upper, a heel attached to;saidupper, said =heel having a recessintheheel-seat engaging surface, and-"a-body comprising particles of-a fine cellular polystyrene resin surrounded by and embedded in a cured resinous glycidyl polylether. filling said-recess and adhering toithewallsof said recess and to .theheel seat of said shoe upperv and portions of said: resinous glycidyl polyether substantially freefrom particles of .saidfinecellular polystw'ene; resin..-.extending out .intothe crevices between 1 the a heeland heel seat .to hold saidheel and shoe upper-firmly together.

10 In. combination; a. shoe-upper -including a shank stiffener with. amend. extending intothe heel-seat portion,

aheelattachedtol said upper having a recess in the heelseat. engaging surface, and a-body. comprising particles of cat-fine cellular. polystyrene resin. surrounded by and" embedded in acured; resinous glycidyl polyetherfilling said irecess=andsurroundingsaid end of saiclshank stifienerland adhering to said ishank stiflener and to the walls of said recess and to the heel seat of said shoe upper-and- .1portions of said resinous glycidyl polyether extending out into;crevicesbetweenwthe heel-and heel-seat to hold said heel; shank stiffener andshoe upper firmly together.

References Citedin the file of this patent- UNITED STATES. PATENTS 2299;195 Ushakofl? Oct. 20,1942 

